Striking the right balance with nitrogen use in farming - Brian Henderson

Admittedly there’s a fair chance you might have missed it, but Scotland last week became the first country in the world to enshrine in law a regularly updated, cross-economy and cross-environment Nitrogen Balance Sheet.

Needless to say farming finds itself very much in the cross-hairs of the document, with food production requiring considerable amounts of this element which, when incorporated into proteins, amino acids and other compounds is one of the key building blocks of virtually all life on earth.

Claiming that the document provides another example of its ‘pioneering and joined up’ approach, the Scottish Government said the nitrogen audit had been promised as part of its climate change proposals.

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And, hinting at what it’s actually for, Environment Minister Mairi McAllan said that the efficient use of nitrogen was important as it helped to maximise the economic benefits whilst minimising any harms that can occur through losses of nitrogen into the environment.

In farming - and indeed global population terms - the upside of synthetic nitrogen fertilisers has been the substantial increases in crop and forage yields since the Haber-Bosch process made the industrial manufacture of synthetic nitrogen fertilisers a commercial proposition more than a hundred years ago - and in the process staved off the Malthusian trap, which many then believed would see the growth in human population inevitably outstrip mankind’s ability to produce enough to feed itself.

But against this major - but often forgotten - plus, the downside of using manufactured nitrogen fertilisers in natural systems - which are always imperfect - can be the release of greenhouse gases which contribute to climate change along with emissions of air and water quality pollutants such as ammonia, nitrous oxide and nitrogen dioxide and run-off and leaching of nitrates from agricultural land.

So while it might not be widely appreciated by the population at large, the farming sector is certainly acutely aware that getting the nitrogen balance right has huge implications for delivering economic, environmental and wellbeing outcomes.

Perhaps never more so than at the moment when the price of manufactured fertiliser has spiralled off the scale, with ammonium nitrate currently standing at around £700 a tonne - close to three times as much as it did at the beginning of the year.

For, while elemental nitrogen is hugely abundant – and in its Inert gas form it accounts for 78% of the Earth’s atmosphere - it requires huge amounts of energy and extreme pressures to push it through the industrial process which will eventually result in fertiliser for plants. And the dramatic rise in energy prices over recent months has been, at least in part, responsible for the spike in fertiliser prices.

The rise in global demand for fertiliser also means farming has plenty of skin in the game of making sure that this extremely expensive product is used as efficiently as possible – so there might be no harm in establishing a baseline for nitrogen use to help the country as a whole, as well as the agricultural the sector, to continue to make improvements and reduce emissions and other losses.

The figures in the SNBS are revealing though – and while the cropping sector shows an estimated nitrogen use efficiency (NUE – and get use to that acronym because I suspect it will soon join the farmers’ lexicon) of 65% might not sound all that optimum, it is compares reasonably well with many other European countries where the range extends from 40-77%. And, in common with most natural processes, the nitrogen cycle means a degree of loss is almost inevitable.

The poor old livestock sector once again comes in for a bit of a battering though when it comes to efficiency, and when considered as a standalone, the balance sheet puts its efficiency down at closer to 10%. Again, while this might sound low it compares with what is achieved on other grazing systems around the world.

However the broadly integrated nature of much of Scotland’s farming means that a lot of the ‘waste’ from the livestock sector is recycled through the use of animal manures which gives an overarching NUE for farming of around 27%.

But, while this balance sheet might be useful tool for policy makers, I strongly suspect that as long as the current fertiliser prices hold sway, it will be another form of balance sheet - the one that shows a business’s bottom line - which will be most prominent in farmers’ minds in the coming years and which will drive improved nitrogen use efficiency.

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